function s = swapCities( cities, nbCitiesToSwap )

s = cities;
n = length(cities);
for i = 1 : nbCitiesToSwap
    city_1 = round(n*rand(1));
    if city_1 < 1 
        city_1 = 1;
    end
    city_2 = round(n*rand(1));
    if city_2 < 1
        city_2 = 1;
    end
    temp = s(city_1);
    s(city_1) = s(city_2);
    s(city_2) = temp;
end

end

